This research will investigate central nervous system regeneration following removal of a population of neurons. Brain damage of this sort is a severe challenge to those who must try to promote recovery in accident victims. A common response to neural trauma is widespread changes in neuron anatomy and connectivity, and some of these changes might promote recovery, if the proper conditions are provided. The rules that govern the regenerative responses of individual neurons can be studied in the relatively simple nervous system of some invertebrates. Knowledge of the neural strategy that is sufficient to restore normal behavior in these animals may point the way to chemical and anatomical manipulations that might promote recovery in the vertebrate nervous system. In the nervous sytem of the adult snail Melampus, removal of one of the two pedal ganglia causes loss of locomotory movements on the operated side. Repair of central tracts and growth of nerves into the denervated side of the foot are correlated with recovery. This research will relate behavioral recovery to the responses of identified neurons remaining in the CNS after pedal ganglion removal. Two mechanisms for reinnervation of the foot are hypothesized: 1) projections from neurons that normally extend out nerves of the missing ganglion from elsewhere in the nervous system could restore function, or 2) neurons in the remaining pedal ganglion and other ganglia that normally have no axons in the contralateral pedal nerves could innervate the periphery. Identified neurons in each category will be penetrated with intracellular recording electrodes and their behavioral role evaluated in semi-intact preparations before dye is introduced to reveal their anatomy. Inputs to the remaining pedal ganglion from the cerebral ganglion on the operated side will be explored with post-recovery lesions and at the level of identified neural connections to determine whether central pathways concerned with the initiation of locomotion have been reassigned during regeneration.